Brake servomotor means



June 15, 1965 R. R. HAGER 3,188,920 l BRAKE sERvoMoToR MEANS Filed April 1, 1965 y 4 sheets-sheet 1 1N VEN TOR. gferg ,waff @LAQ/@m Arroz/145V June 15, 1965 R. R. HAGER 3,188,920

BRAKE SERVOMOTOR MEANS Filed April l, 1963 4 Sheets-Sheet 2 INVENTOR @mgm June 15, 1965 R. R, HAGER v 3,188,920

BRAKE SERVOMOTOR MEANS yFiled April 1, 196s 4 sheets-sheet 5 INVENTOR 49066878 H4669 mig June 15, 1965 R. R. HAGER 3,188,920

BRAKE SERVOMOTOR MEANS Filed April l, 1963 4 Sheets-Sheet 4 IN VEN TOR.

United States Patent O 3,188,920 BRAKE SERVOMOTOR MEANS Robert R. Hager, South Bend, Ind., assignor to The Bendix Corporation, South Bend, Ind., a corporation of Delaware l Filed Apr. 1, 1963, Ser. No. 269,240

4 Claims. (Cl. 91-391) This invention relates to a power braking mechanism yand,'more particularly, to a pneumatic power brake device having means to sense stroking distance to accord `an operator with a sense of brake system condition.

In power brake systems as applied to vehicles, it has ,usually been the intent of designers to reduce the stroke necessary` for a brake pedal while at the same time providing feel or awareness -of brake application. Such designs center aboutservomotors having means to magnify braking force with a pressure responsive member whose travel is only limited by the servomotor chamber dimensions. The operator will feel the effect of braking, but will not have any way of knowing how much travel is necessary to operate the vehicles brake shoes unless power has failed and manual control has taken over. Under such situations of power failure dire consequences have arisen because of worn brake shoes. It is, therefore, the principal intent of my invention to provide an indication under power conditions that would forewarn a vehicle operator of worn brake shoes and the like which cause excessive travel of brake applicators.

- In more detail,` it is an object of my invention to increase the stroke of a brake pedal when the brake shoes have Worn beyond reasonable limits by sensing the travel of a servomotor controlled device building up braking pressure.

Another object of my invention is to sense the position of a pressure 'responsive member in a servomotor to control the holding of a manually operable element in an extended position or to allow telescoping of the element within the servomotor when the member has an abnormal travel.

Other objects and advantages will become readily apparent to those skilled in the art to which this 'invention relates from the following description of the accompanying drawings in which:

' FIGURE l is a sectional side view of a servomotor constructed in accordance with the principles of my invention showing the power section in a rest or nonactuated condition; FIGURE 2'is another sectional side view of the servomotor showing the power section energized such that the control rod is telescoped within the servomotor indicating an abnormal travel of the power section has occurred;

FIGURE 43 is'a broken plan view of my servomotor presenting details of a valve actuation means for con trolling the holding or telescoping of a manually operable control member; and

FIGURE 4 is an end view of my servomotor showing passage location within the housing.

Inh more detail and with reference first to FIGURE 1, I show a servomotor having a housing consisting of a frontend wall 12, a rear end wall 14, and an intermediate section 16 all of which are joined together by bolts 18 and 20 and a spacer 22. The spacer 22 is adapted to sealingly hold a pair of diaphragms 24 and 26 against the intermediate section and the rear end wall 14, respectively.

The diaphragms 24` and 26 are provided with slots which are of a depth and cross-section to form an interference iit with in-turned flanges 28 and 30 of a pair of movable walls 32 and 34, respectively. These movable walls are sealingly connected to a valve housing 36 as will be explained hereinafter in greater detail.

As seen in FIGURE 1, the valve housing is constructed of two tubular portions 38 and 40 which are welded together and for purposes of description, termed front and rear portions, respectively. The rear portion 40 is provided with a side opening 42 and a hose connection port 44, and a valve body 46 is buttressed against a forward end wall 48 of the rear portion 40 with a rubber disc 50 interposed. Adjacent the disc, the valve body is yprovided with an opening 52 whose diameter may vary in accordance with reaction requirements of the power brake system. The end wall 48 is provided with an opening 54 to communicate the interior of portion 40 with the interior of portion 38. In addition, as seen, the rear portion is formed with radiating portions opposite the end wall 48 which terminate in the in-turned flanges 30 sealingly gripped by the diaphragm 26. Y

The portion 38 s closed forwardly by a sleeve end closure 56 which sleeve is joined to portion 3S by a resilient collar 58 and retainer ring 60. A seal 62 having a tubular extension 64 adapted to have a rolling interference t with sleeve 56 provides an operative connection through the front end wall 12. The tubular extension is also adapted to receive an annular flange 66 of the movable wall 32 to apportion the servomotor into a front chamber 68 and a rear chamber 70. The sleeve end closure is provided with radial drilled passages 74 to open the interior of portion 38 to a low pressure source or atmosphere exterior of the servomotor 10 depending on how one is to utilize my invention.

The valve body 46 slidably mounts a valve poppet seat member 76 in opening 52, and by a diaphragm 78 a poppet sleeve 80 carrying a front valve face 82 and a rear valve face 84 bonded to washer members 86 and 88 which are held on the sleeve as by riveting, press titting, etc. A control member 90 is aixed to member 76 as by screwing, pinning, etc., and movably mounted at its opposite end with respect to the body 46 by adiaphragm 92. This control member mounts a control rod 94 by a ball-joint connection, as shown, which control rod is operatively connected to a brake pedal (not shown) within a vehicle. The valve body 46 is formed with a rearwardly facing valve seat 96 and a valve stop member 98 to limit the rearward travel of the valve sleeve 80.

In the non-energized position, as shown by FIGURE l, the valve sleeve 80 allows communication of chamber 70 with chambers 68 and 72 by way of passages 100 and 102 (see FIGURES 2 and 3) in the intermediate section 16 and spacer 22, which chambers are in ow communication by way of a tubular member 104 and a cavity 106 in front end wall 12 and a hose connection 107 (see FIGURES l, 2 and 3). The intermediate section and spacer is provided with another passage 108 (see FIGURE l) which is connected to a high pressure source by way of a conduit 110 via port 112, which high pressure source may be atmosphere or compressed air depending on how the connection to the openings 74, as above-mentioned. The passage 108 opens into chamber 70 at one end and to an opening 112 through end wall 12 at the other end, which opening 112 leads to a control chamber 114.formed exteriorly of front end wall 12 by a cover 116 over the cavity 106. A valve plug,118 is biased by a spring 120 to seat on a plate 122 to control communication of chamber 114 and cavity 106. v The tubular member 104 is slidably mounted in the wall 12 and arranged to cooperate with the plug 118 to lift the plug from the plate 122 under conditions hereinafter explained.

Before proceeding to a description of the operation it should be noted that I provide a spring 124 between kformed the end wall V12'with alug einsasaol Y, n`V

the end wall 12' and the movable wall 32 to bias the latter rearwardly. In addition, by the use of diaphragms y 78 andy 92 I have eliminated thelneed rfor several seals and a` heavy return spring.y In other wordsfIprovridea uid pressure means forA Vbiasing the valve' mechanism Yto its .normal non-operative position as seen. lin FIGURE -l. More particularly, the area of diaphragmy 78' exposed to high pressure uid plus the frontal area of valve vface 82.*exposed to the same fluid isless than'the area vof diaphragm 92' subjected to' thesame pressure. This Vin placev of one of theV many springs used in rprior art units. y Thus, the return stop 98 for the valve structure is applied to the sleeve 80 on'retainer ring 88 and the ret turn spring126 to the mem-ber 76to establish the original bias on vthe sleeve sothat enough differential can be devrelationship of pressure biasing'the valve structuregto the rear is maintained throughout .valve operation.v As 'maybe realized'byrthose skilled in the art the use of diaphragms reduces frictionand hysteresisof eration normally attributable to sliding seals; VItis also suggested that an internalspring 126 `be .incorporated be-,

tween the valve body 46iv andthe seat 'member 76.V l

By way of reference toV FIGURE 3`, my mechanism for actuating the tubular member 104 is`v shownV comprising a Y trigger 128arranged to cooperate with an abutment por- `As seen, the triggerV is 12 and Ybiasedfby a tion 130v of the movable wall3t2.Y slidably mounted throughthe wallY spring' 1'32., which rotatably supports a vshaft 134 t-ofwh'ich'V-l' have rotatably aixed a lever 136 and xedly lmounted a lever 138.. 'Iwihe levers are normally positionedsuchk that their terminal ends, Vas

l projected from said shaf-tflie inthe same plane, and a spring 140 connects these Yterminalends'.` r[Fhewall 12 isV Y also provided with stops 142 and"l lever V136; The triggery 128is necked, as.' at 146, withV 144; to vlimit'V travel of vfveloped on the biasing vdiaphragms toY cause the-valve towork. Otherwise a restriction would have to be designed in the unit so that supply airpressure of whatever typeused could be builtup fast enough to create a bias lto cau-se the valve to seal. f Such restrictions tend to slow VVTesponse of' units of this type and thereforejarenot desir.- K c( v able. Y

In'the event that adequatebraking of the associated ve'- hicle requires the Vwall 32 to stroke until itfcontac'ts trigger Y 128' (see FIGURE 2).V and forces this trigger forwardly 13f1ft-o1project into chamber., 68. yI have also Ybeveled faces cooperating with shearing-'face 'enlever-136;' f

' In operation, airl pressureis supplied directly to the pas- V sage 108 leading'tol chambers 70y and-114 (seeF-IGUKlEE Yl). From chamber'70 .the-pressurized.,fluid or atmospheric air, asthe case may be,passes into the-*valve heus-f f ing 36 via opening42 to port 44 thence'through -tube orhoseconnection107 and bet-weenthe seat 96. and ring V84 (see FIGUR-E 3) to passage100 leadingtochamber 68;.y From the chamber 68 the fluid passesthrough tube 10ft-to cavity 106 andV passage-1012 (see-FIGURE'Z) to chamber72..' y As seen; a seal 14S-for the Vrear wall 14 and the seal 58 on the tube section 38 are'ofa different size suchth-at the neteffect of p similar pressures Vacting-thereat'V isto'bias the valve` housing' and wall 34-toabut the.' wall 14,-- Yas seen in FIGURE l. Y

lForcet applied to control rod 94 closes ring"84gon seat 96v and opens vthe exhaust poppet member l76 to allow fluid pressure` in chambersl 68 and- 72 to exitor be drawnfrom port or-opening 74 bytheway to movewall 32 forwardly and'V hold wall` 34 rearwardly which will proJect a :forcetransmit-tingrod `1x50 from withinmy servomotor.V vThe, rod 150mayf-or purposes of illustration-be attached 'to a-master cylinder ;piston, as maybe readily understood by those skilledsin the art. g'

T-he force transmitting rod and'm-as-ter cylinder, connecovfopening'St.l .This creates a pressure differential across the diaphragrns 24 and 261 In any event, the pressureidifferential across/wall -the forcfeist-roking, and displacing fluid. from" 'a'maste'r cylinder;` whereas, the pressure.. differential'facrossthe rear wall 34 willA cause portionf40to compress. disc 50 l Y andpextrude it into opening 5`2fto react onmember 76to Y provide feel toV rody 94V. However, this reaction force is also applied through body *461:0 the rear wall 1`4 to split the` forcea'nd obtain not the total feel but a desired feel which can 4be increased-or Y be readilyexpected the diaphragm area-26y eanfbel varied utilize a disc reaction.

decreased by respectively in'- f creasing or decreasing'the size. of' opening 52.2- Alsjmay Y a'gainstfthe spring 131, it 4will causelever 136,' to revolve to stretch spring l1,40. 'This places a maximum tensileload v on-the` spring which is vrelieved by snapping lever 138 to rforce'tube 104 inwardlyre-moving plug'118 from plate 122. 'n The stop--144y limits the stroke Yof trigger; 128 to preclude spring from'opposin'g 'spring 131 preventing return ot' trigger .128 when brakes are released.' AWhen plug ll-rrioveszoifplate 122'cavity 106 and chamber 114 are in communication' and chambers 70 and 72 arel equally pressurized'to create a zero pressure differential across Ywall v34. With the absence of any pressure differential the valve housing will now follow-up the front diaphragm Vandthe operatorfeels Ithisaction yasstrokey on the pedal connected to'r-odr-94," yThe spring 13-1-Vr`et'rips the ltrigger L128 when force onjrod 94-is released and wall 32 is revturned' by Vspring 1724. r Instead Vof(-` having spring 131 for the above description butrather by the appended'claims which set forth the true scope of my invention.

y:If claim: j Y gV 1. yIn a pressure suspended' servomotor includingv acont'rol rod anda" force transmitting rod, a mechanism indicating abnormal travel of saidrforce transmitting rod, which mechanism"corr'lprises:`V i f' a housinghaving a' pressure inletl with a first iluid'passage connected thereto, a second fluid passage therein, a third iluidrpassa'ge therein, said first and second passages-extending throghfone end'of the housing, Y and axially aligned openings in'said housing adapted 'to'sealinglyreceivefat respectiveend's, said control Irod and said force transmit-ting rod;` i a rsti'movablwall in said housing dividing said housing into a first variable volume chamber and a sec- Vond `variable vvolume chamber having ow cornmunication Awith, "said first and secondV iluidl passages, respectively;

Y a secondjmovable walliri said Vsecond.varial'nle .volume chamber Ydividing a third "variable volume Vchamber fromxsaid second'chamber such that said Vsecond chamber is connected `to'said iir'stfluid passage and Vsaid third chamber isin'flow communication with Y said second passage; g v l aV valve housing opera-tively connected to saidrst and second movable walls, said valvei housing having an axial passage l'eadingto` a low pressure port, at one fen-d, a radial passagejfcommunicating'said second chamber to the interi-orf of said ,valve housing Vandi` an outlet port in said housing;I means for ycommunicating said Y valve holrlsing'` outlet port lto said third .fluid passage which third passage isopenitosaid-rst chamber;` l' f v "val-ve, operatiyely mounted j* in Asaid valve-` housing, which valve` is adapted tob'e controlled by saidtconxtrol rod to open and close communication` between said radial passage and said low pressure port via said axial passage and between said radial passage and said outlet port, whereby said first chamber is communicated to a low pressure and to a pressure in s-aid second chamber, respectively;

a means sensing the travel of said iirst movable wall attached to an end wall of said housing, said means adapted to control iow communication between said first, second and third iiuid passages.

2. 'For a pressure suspended operable element and a driven element operatively connected in a servomotor, a device to sense travel of said driven element in excess of a predetermined distance, said device comprising:

a housing having a chamber therein with a front and a rear end wall joined by an intermediate section, said section having three passages therein first of which registers with a passage through said front end wall, a second of which registers with an inwardly directed passage in said .front end wall leading to la bore through said front Wall with a third passage having a port adjacent said front end wall and another port intermediate said chamber, said front and rear Walls having additional axial, aligned openings;

a means to separate said chamber into intermediate, rear and front variable volume chambers each of which is communicated respectively to said iirst passage, said second passage and said third passage in said intermediate section;

a valve housing sealingly mounted in said axial, aligned openings, and operatively connected to said means to separate said chamber into front, rear and intermediate variable volume chambers, said valve housing having an axial passage, a control pressure port communicating said intermediate variable volume chamber to said axial passage, a passage port connecting said axial passage with said intermediate port of said passage of said intermediate section opening into the chamber adjacent said `front wall, and a low pressure port communicating said axial passage with a low pressure source;

a valve means controlling communication of said passages of said intermediate section; and

a tubular means mounted through said front end wall, said tubular means sensing the distance said driven element travels, and adapted to control said second valve to close communication of said front and rear chambers and open communication between said intermediate and rear chambers whereby said manually 'operable element is drawn into said servomotor to provide an indication to an operator of an abnormal condition.

i3. For a pressure suspended servomotor including a manually operable element controlling a valve means to operate a pressure responsive member, which member is operatively connected to a force transmitting means, which means is also operatively connected to said manually operable element, a pressure responsive device to indicate abnormal travel of the force transmitting means, which device comprises:

a movable wall operatively connected to both the manually operable element and the force transmitting means;

first passage means within said servomotor to convey a high pressure to one side of said movable wall;

a second passage means Within said servomotor to convey a low pressure to the other `side of said movable wall, whereby a pressure dilierential across said wall is created to bias the manually operable element to a rear position; and

a valve means operatively connected to the servomotor, which means is responsive to extreme stroking of said servomotor and arranged to create equal pressure on said movable wall through said iirst passage means and said second passage means to decrease said pressure differential to draw the manually 0perable element inwardly of said rear position whereupon an operator is made aware of the abnormal stroking.

4. in a power braking system for vehicle brakes, a

servomotor comprising:

a housing comprised of a front end wall, a rear end wall and an intermediate section joined together to form a power chamber in which a pressure responsive element is operatively mounted, said servomotor additionally including a manually operable element and a driven element operatively slidably mounted by said rear end wall and said front end wall respectively, said driven element being connected to both said pressure responsive element and said manually operable element;

a valve means operatively connected to said manually operable element, said valve means normally providing equal pressure to each side of said pressure responsive element and having provision to, at the urging of said manually operable element, reduce pressure on said pressure responsive element on the side facing said front end Wall to project said driven element;

a cavity in said rear end wall open to the area of said servomotor behind said pressure responsive element;

a movable wall in said cavity dividing it into a front and a rear variable volume chamber, said wall being operatively connected to said manually operable element;

passage means in said servomotor providing flow cornmunication of the 4area adjacent said front end Wall with the rear chamber such that said movable wall is normally biased by pressure in said area behind said movable wall to hold said manually operable element in its extended position; and

means to control said passage means in accordance with the stroking of said servomotor to close 0H. said communication with said area adjacent said front end wall and open communication between said area 'adjacent said rear end wall and said rear chamber whereupon pressure on said manually operable element is no longer resisted and said element is allowed vto telescope inside said servomotor to provide an indication of said stroking.

References Cited by the Examiner UNITED STATES PATENTS FRED E. ENGELTHALER, Primary Examiner.

SAMUEL LEVINE, Examiner. 

1. IN A PRESSURE SUSPENDED SERVOMOTOR INCLUDING A CONTROL ROD AND A FORCE TRANSMITTING ROD, A MECHANISM INDICATING ABNORMAL TRAVEL OF SAID FORCE TRANSMITTING ROD, WHICH MECHANISM COMPRISES: A HOUSING HAVING A PRESSURE INLET WITH A FIRST FLUID PASSAGE CONNECTED THERETO, A SECOND FLUID PASSAGE THEREIN, A THIRD FLUID PASSAGE THEREIN, SAID FIRST AND SECOND PASSAGES EXTENDING THROUGH ONE END OF THE HOUSING, AND AXIALLY ALIGNED OPENINGS IN SAID HOUSING ADAPTED TO SEALINGLY RECEIVE, AT RESPECTIVE ENDS, SAID CONTROL ROD AND SAID FORCE TRANSMITTING ROD; A FIRST MOVABLE WALL IN SAID HOUSING DIVIDING SAID HOUSING INTO A FIRST VARIABLE VOLUME CHAMBER AND A SECOND VARIABLE WITH SAID FIRST AND SECOND FLUID PASSAGES, MUNICTION WITH SAID FIRST AND SECOND FLUID PSSAGES, RESPECTIVELY; A SECOND MOVABLE WALLIN SAID SECOND VARIABLE VOLUME CHAMBER DIVIDING A THIRD VARIABLE VOLUME CHAMBER FROM SAID SECOND CHAMBER SUCH THAT SAID SECOND CHAMBER IS CONNECTED TO SAID FIRST FLUID PASSAGE AND SAID THIRD CHAMBER IS IN FLOW COMMUNICATION WITH SAID SECOND PASSAGE; A VALVE HOUSING OPERATIVELY CONNECTED TO SAID FIRST AND SECOND MOVABLE WALLS, SAID VALVE HOUSING HAVING AN AXIAL PASSAGE LEADING TO A LOW PRESSURE PORT AT ONE END, A RADIAL PASSAGE COMMUNICATING SAID SECOND CHAMBER TO THE INTERIOR OF SAID VALVE HOUSING AND AN OUTLET PORT IN SAID HOUSING; A MEANS FOR COMMUNICATING SAID VALVE HOUSING OUTLET PORT TO SAID THIRD FLUID PASSAGE WHICH THIRD PASSAGE IS OPEN TO SAID FIRST CHAMBER; A VALVE OPERATIVELY MOUNTED IN SAID VALVE HOUSING, WHICH VALVE IS ADAPTED TO BE CONTROLLED BY SAID CONTROL ROD TO OPEN AND CLOSE COMMUNICATION BETWEEN SAID RADIAL PASSAGE AND SAID LOW PRESSURE VIA SAID AXIAL PASSAGE AND BETWEEN SAID RADIAL PASSAGE AND SAID OUTLET PORT, WHEREBY SAID FIRST CHAMBER IS COMMUNICATED TO A LOW PRESSURE AND TO A PRESSURE IN SAID SECOND CHAMBER, RESPECTIVELY; A MEANS SENSING THE TRAVEL OF SAID FIRST MOVABLE WALL ATTACHED TO AN END WALL OF SAID HOUSING, SAID MEANS ADAPTED TO CONTROL FLOW COMMUNICATION BETWEEN SAID FIRST, SECOND AND THIRD FLUID PASSAGES. 